o:1506 Philopatry yields higher fitness than dispersal in a cooperative breeder with sex-specific life history trajectories en Social evolution is tightly linked to dispersal decisions, but the ecological and social factors selecting for philopatry or dispersal often remain obscure. Elucidating selection mechanisms underlying alternative life histories requires measurement of fitness effects in the wild. We report on a long-term field study of 496 individually marked cooperatively breeding fish, showing that philopatry is beneficial as it increases breeding tenure and lifetime reproductive success in both sexes. Dispersers predominantly join established groups and end up in smaller groups when they ascend to dominance. Life history trajectories are sex specific, with males growing faster, dying earlier, and dispersing more, whereas females more likely inherit a breeding position. Increased male dispersal does not seem to reflect an adaptive preference but rather sex-specific differences in intrasexual competition. Cooperative groups may thus be maintained because of inherent benefits of philopatry, of which females seem to get the greater share in social cichlids. Biased Dispersal; Cichlid Fish; Habitat Saturation; Broodcare Helpers; Delayed Dispersal; Group-Size; Ecological Constraints; Territory Quality; Reproductive Skew; Direct Benefits 1552099 10.1126/sciadv.add2146 2023-04-14T13:39:29.676Z 44 yes 46 Arne Jungwirth University of Veterinary Medicine, Vienna / University of Bern 0000-0002-2962-4015 Michael Taborsky University of Bern / Max Planck Institute of Animal Behavior / Institute for Advanced Study Berlin person 0000-0002-1357-4316 Joachim G Frommen University of Bern / Manchester Metropolitan University person 0000-0002-1752-6944 Dario Josi University of Bern / Eawag Swiss Federal Institute of Aquatic Science and Technology person 0000-0003-4543-4438 Danielle Bonfils University of Bern person Markus Zöttl University of Bern / Linnaeus University person 0000-0002-5582-2306 application/pdf 821855 https://phaidra.vetmeduni.ac.at/o:1506 no yes 17 70 1552253 Science Advances 11 9 9 American Association for the Advancement of Science 2023